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76 lines
1.6 KiB
ArmAsm
76 lines
1.6 KiB
ArmAsm
;
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; IRQ handling (ATARI version)
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;
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.export initirq, doneirq
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.import callirq
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.include "atari.inc"
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.ifdef __ATARIXL__
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.import __CHARGEN_START__
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.include "romswitch.inc"
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.endif
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; ------------------------------------------------------------------------
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.segment "INIT"
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initirq:
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lda VVBLKI
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ldx VVBLKI+1
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sta IRQInd+1
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stx IRQInd+2
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lda #6
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ldy #<IRQStub
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ldx #>IRQStub
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jsr SETVBV
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rts
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; ------------------------------------------------------------------------
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.code
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doneirq:
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lda #6
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ldy IRQInd+1
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ldx IRQInd+2
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jsr SETVBV
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rts
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; ------------------------------------------------------------------------
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.segment "LOWCODE"
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IRQStub:
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cld ; Just to be sure
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.ifdef __ATARIXL__
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pha
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.ifdef CHARGEN_RELOC
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lda CHBAS
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pha
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.endif
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lda PORTB
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pha
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and #$FE
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sta PORTB ; disable ROM
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set_chbase >__CHARGEN_START__
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.endif
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jsr callirq ; Call the functions
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.ifdef __ATARIXL__
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pla
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sta PORTB ; restore old ROM setting
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.ifdef CHARGEN_RELOC
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pla
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sta CHBAS
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sta CHBASE
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.endif
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pla
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.endif
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jmp IRQInd ; Jump to the saved IRQ vector
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; ------------------------------------------------------------------------
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.data
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IRQInd: jmp $0000
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